These studies are designed to elucidate the roles of messenger RNA, ribosomal RNA, ribonucleoprotein particles, and unusual phosphorylated nucleotides in the control of compensatory renal hypertrophy and to examine some of the potential stimuli. The hypothesis that mRNA lacking polyadenylate tracts accumulates during hypertrophy will be examined using chromatographic methods for rapidly discriminating poly(A) mRNA; the role of "caps" on the 5'-end will be examined. Equilibria between cytoplasmic free mRNP and polysome-associated mRNP will be established in different phases of growth. Conservation of mature rRNA as a major mechanism in increasing the average cellular amount of rRNA will be tested further by concurrent studies of ribosomal protein metabolism. Since unusual highly phosphorylated nucleotides may be a control for rRNA synthesis, their function is to be studied. Finally, the availability of pristine high-molecular-weight so-called nerve growth factor, which concentrates rapidly in kidney and has many of the characteristics of the putative stimulatory substance, will permit examination of a pure growth-regulatory substance in kidney. Proteins synthesized in liver and absorbed by the kidneys may also be studied in this respect. Clinical extensions of these data may provide a basis for quantitating and controlling growth in a diseased or transplanted kidney. They also provide a framework for isolating mRNAs for renal proteins such as erythropoietin and renin.